A biotechnologist wanted to create a colony of E.coli possessing the plasmid pBR322, sensitive to Tetracycline. Which one of the following restriction sites would he use to ligate a foreign DNA ?

Options

A. Sal I
B. Pvu I
C. Eco RI
D. Hind III

Explanation

To solve the question regarding the creation of a colony of E. coli possessing the plasmid pBR322 that is sensitive to Tetracycline, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Objective**: The biotechnologist wants to create a colony of E. coli that is sensitive to Tetracycline. This means that the E. coli must lose its resistance to Tetracycline.

2. **Identify the Plasmid**: The plasmid in question is pBR322. This plasmid contains genes that confer resistance to antibiotics, including Tetracycline.

3. **Locate the Restriction Sites**: The pBR322 plasmid has specific restriction sites where foreign DNA can be inserted. The relevant sites include:
- BamHI
- SalI
- EcoRI
- HindIII
- PvuI

4. **Determine the Impact of Insertion**: To make the E. coli sensitive to Tetracycline, the foreign DNA must be inserted into the Tetracycline resistance gene. This will disrupt the gene, leading to the loss of resistance.

5. **Identify the Correct Restriction Site**:
- The BamHI and SalI sites are located within the Tetracycline resistance gene.
- Inserting foreign DNA at either of these sites will disrupt the gene and make the E. coli sensitive to Tetracycline.
- The question asks for one restriction site, and since SalI is mentioned, we will choose that.

6. **Conclusion**: The biotechnologist should use the SalI restriction site to ligate the foreign DNA, as it will effectively disrupt the Tetracycline resistance gene in pBR322.

### Final Answer:
The restriction site that should be used to ligate the foreign DNA is **SalI**.

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